A peristaltic pump is a type of positive displacement pump used for pumping a variety of fluids. The fluid is contained within a flexible tube fitted inside a head with a circular casing. A rotor within the head, with at least two rollers attached to the external circumference of the rotor, compresses the flexible tube against the circular casing. As the rotor turns, the part of tube under compression closes, forcing the fluid to move through the tube. As the tube opens to its natural state after the passing of the roller, restitution fluid flow is induced to the pump.
In a peristaltic pump, the only part of the pump in contact with the fluid being pumped is the interior of the tube. This eliminates the possibility for contamination getting into the fluid and makes it is easy to clean the inside surfaces of the pump. Furthermore, since there are no moving parts in contact with the fluid, peristaltic pumps are inexpensive to manufacture. Their lack of valves, seals and glands makes them comparatively inexpensive to maintain, and the use of a hose or tube makes for a relatively low-cost maintenance item compared to other pump types.
Peristaltic pumps are mainly used to pump clean or sterile fluids because the pump cannot contaminate the fluid. Peristaltic pumps can also be used to pump aggressive fluids because the fluid cannot contaminate the pump. Therefore, peristaltic pumps should be used where isolation of the fluid from the pump and the environment, and/or isolation of the pump from the fluid, is critical.
The Flexography industry has quickly adapted the use of peristaltic pumps for many reasons. When used in a flexographic printing press, a peristaltic pump is more economical, provides faster cleaning times, wastes fewer printing inks, and contaminates fewer printing inks. In a flexographic printing press, the ink needs to be isolated from the pump and its environment to be free of contaminates in order to function properly in printing. The ink also needs to be isolated from the pump to keep the pump functional and clean. Thus, a peristaltic pump is ideal for a flexographic printing press.
Some prior art patents that show a peristaltic pump head used in the Flexography printing industry include: U.S. Pat. No. 6,041,709, issued to Wells on Mar. 28, 2000, Inc.; U.S. Pat. No. 5,630,711 issued to Luedtke on May 20, 1997; and U.S. Pat. No. 4,552,516 issued to Stanley on Nov. 12, 1985.
There are many problems with the current peristaltic pump head when used in moving a fluid or delivering ink to a flexographic printing press. The peristaltic pump heads consist of plastics and other materials, which cause constant material failures when used in moving fluids in the flexographic printing environment or any environment. These failures of materials are a very expensive cost because they require maintenance and slow down production with more pump downtime. This type of pump operation is very costly to the Flexography industry where cleaning and down time is a major part of the Flexography industry cost. The current designs are very expensive when designed as heavy industry systems to overcome these failures. These systems take up a great deal of space, require periodic maintenance and are not operator friendly.
Current peristaltic pump heads may include adjustment fixtures, occlusion knobs, bladders, and other things which are attempts to prolong tube life. These things are inadequate and do not solve many problems encountered with the tube, including: the cumbersome loading and adjusting of the tube (requiring the use of tools to adjust and load the tube), tube fatigue (from the tube being compressed repeatedly) which wears down the tube and lowers the expected tube life, tube creep (the tube becomes off centered with the rollers due to hydraulic forces caused by peristalsis) which causes additional wearing down of the tube, and tube bunching or gathering at the exit of the pump head (caused from the tube being stretched towards the exit from the rollers) which causes additional wearing down of the tube and can lead to tube rupture when used for several hours of operation. These problems lead to constant tube failures and require frequent replacement of the tube. The replacement of peristaltic pump tubes in existing pumps is a difficult and time consuming procedure which forces excess down time in the Flexography printing industry.
Accordingly, an object of this invention is to address all of these problems.
In particular, the aim of the present invention is to provide a peristaltic pump head which allows easy loading of the tube, a pump head with simple parts that are easy to manufacture and maintain, and a pump head that promotes long life for the pumping tube. The present invention will allow a peristaltic pump which is characterized by its simplicity, durability, low cost to the industry, and ease of manufacturing, servicing and versatility.